Electric-circuit breaker



Feb. 14, 1928.

F. W. ALDER ET AL' ELECTRIC CIRCUIT BREAKER 174 057? EN!) 5'. M Begum/ V F. w. LDER ET AL ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Feb.24, 1920 s./\ 54 4 by M flftorneys.

Patented Feb. 14, 1 92 8.

TES PATENT OFFICE.

OF PALO ALTO,

TELEGRAPH COMPANY, OF FRANCISCO, CALI- FORNIA, A oonronnrroiv or CALIFORNIA.

ELECTRIC-CIRCUIT B'nEAKER.

Application. filed February The invention relates to devices for openin electric circuits. upon the presence of deiterious conditions in the circuits.

An object of the invention is to provide 6 an automatic circuit breaker in which all i of the separable contacts are submerged in oil.

Another object of the invention is to provide a circuit breaker having means operalu tive directly under short circuiting conditions and indirectly on ordinary excessive overload conditions to open the circuit.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the followin description where we shall outline in in that form of the invention which we have selected for illustration in the drawings accompanying and forming part of the present specification. In said drawings, we have shown one form of circuit breaker of our invention, but it is to be understood that we do notv limit ourselves to such form, since the invention, as expressed in the claim, may be'embodied in a plurality of forms.

Referring to said drawings: Figure 1 is a perspective view ofthe circuit breaker in its enclosing case.

igure 2 is a vertical section through. the circuit breaker looking from the rear and showingthe switch mechanism.

Figure 3 is a vertical section through the circuit breaker looking from the front and showing the automatic controlling mechanism.

Figure 4 is a diagrammatic representation of the circuits of the device.

The circuit breaker of our invention comprises an enclosing casing consisting of the upper section 2, the cover 3 and the lower section or oil tank 4. The upper section 2 is provided at its sides, adjacent the lower end thereof, with dependent plates 5,; secured to and spaced inwardly from the sides and depending below the lower edge thereof. The sides of the tank 4 extend up into the spaces between the sides of the up er section and the plates, forming a tig t joint therewith, and the tank is held in place by set screws. g

The lower edges of the plates 5 are bent inwardly to form an angle and secured to the angle is a block 6 of insulating material to which the stationary contact clips 7 24, 1920. Serial No. 360,715.

are secured by bolts 8 which serve as bind .ing posts for the lead Wires. The present circuit breaker is .designed for installation in a three-phase, three-wire circuit and is provided with three pairs of contacts, one pair being in each legv of the circuit. Arranged below the block 6 and spaced therefrom is a bar 9 of insulating material to which the contacts 12 are secured. The bar 9 is secured to the slide rods 13 which pass through the block 6 and guide bushings .14 thereon and which are connected together above the block by the cross-bar 15. Springs 16 surrounding the rods 13 and interposed between the block 6 and the bar 9 hold the bar 9 depressed and return it to its depressed position when it is released in its elevated position.

The bar 9 handle 17, which is secured to a crank-rod 18 extendin g through the upper casing and having a portion 19 thereof ofi-set from the axis of rotation of the rod. When the handle is moved about the axis of the rod, the off-set portion 19 engages and forces upward the cross-bar 15 raising the contacts 12 into engagement with the contacts 7 and closing the circuit. The central contact 12 is connected to the binding post 21 by the flexible conductor 22 and the outer. contacts 12 are connected to the binding posts 23 through the flexible conductors 24 and the solenoids 25 and 26, the solenoids thus being connect ed in series in the circuit.

Means are provided for holding the crank rod in position to hold the switch closed and for releasing the switch conditions obtain in the circuit. Pivoted within the upper casing on the pivot 27 is a ,lever 28 provided on its inner end with a.

counterwei ht 29 and extending at its other end throug the side wall of the casing. The lever is jacent the counterweight, with a notch or seat 31 in which the ofi' -set portion 19 of the crank rod engages; when, the crank rod when deleterious provided on its under surface, ad

is raised by movement of the is rotated to fully close the switch. The

crank rod is held inits raised position by engagement in the notch 31. The outer end of the lever 28 is provided with an aperture through which the stem 32 of the core 33 of the solenoid 34 passes. The solenoid 34, which we have termed the low-voltage solenoid, is connected across two legs of the circuit and when the switch is closed, the solenoid 1s energized, raising the core 33 and relieving the lever 28 of the weight thereof. Should the voltage in the circuit decrease below a predetermined value, the magnetomotive-force of the solenoid is insuificient to hold the core 33 elevated and it drops, tripping the latch lever 28.,and perhitting the switch to spring open. The stem 32 is provided on its upper end with a knob which may be struck to depress the stem and release the switch. Arranged in series in two legs of the ci'rcuit, are solenoids 25-26 provided with cores 36-37 carrying stems 3839. Mounted on the stem and insulated therefrom are contact discs 41-42 pressed downward against stops 43, by springs 44. Disposed beneath and normally engaged by the discs 4142 are contacts 45, 46, 47 and 48, the contacts 45,

41 and contacts 47, 48 being associated with disc 42. Contact 45 is connected to one leg of the circuit; contact46 is connected to contact 47 and contact 48 is connected to the solenoid 34, the other end of which is connected to the other leg of a circuit. The solenoid 34 is, line and its circuit is provided with two points of breakage. An excessive [current in one circuit will cause the solenoid, in series in the circuit, tolift the associated. contact disc and open the circuit of the solenoid 34, allowing the core therein to drop and trip the latch-lever 28. The springs 44 which press the contact discs. against the contacts are light springs which are sufliciently resilient to permit the stems 38 and 39 to vibrate vertically due to an alternatin electromotive force in the solen oids without imparting the vibrations to the discs, which would cause an interruption of the low voltage solenoid circuit.

Means independent of the solenoid 34 are provided for opening the circuit upon the presence of a great overload, suchas occurs on short circuiting. The stem 38 of the solenoid 25 extends upward through an aperture in counterweight 29 secured to the latch 28 and is provided below the counterweight with a stop 51 which strikes the counter- 46 being associated with disc' therefore connected across the.

weight as the stem is abruptly raised, raisthe circuit.

. The tank 4 is filled with oil to a suflicient height to submerge the contact discs, so that all points of circuit interruption are submerged in oil, thereby insuring-clean breaks and the absence of sparking.

By the circuit breaker of our invention,

the circuit is opened, due to a reduction in line voltage to a predetermined value, by an overload of sufiicient magnitude which if continued would injure the motor, and by an excessive overload, such as is due to short circuiting conditions. The circuit-breaker shown is designed for use in. a three-phase, three-wire system and will operate to prevent motor burnout-s due to single phasing. Should'one phasebe opened, the increased current in the other phase will cause the low voltage solenoid circuit to be opened and the switch released.

We claim;

In an electric circuit breaker for a polyphase circuit, a movable contact-carrying bar, a lever for moving said bar to closed circuit position, a latch for holding the bar in such position, a solenoid associated with said. latch and connected across two legsof the-circuit, said solenoid operating when deenergized spaced contacts in the solenoid circuit and normally closing, said circuit, a solenoid ar-' ranged in series in each of said legs, a core FRANK w. ALDER. i SYDNEY N. BARUCH.

to trip said latch, two pairs of 

